2 days with no eggs

Before I start, I want to assure you that I HAVE read the sticky about egg production problems....I think I just need some help walking through this to be sure everything is okay.

We have 4 hens (no roos) in a coop with a run: 2 EE's, 1 BA, & 1 BO. We bought them from a feed store on March 19, 2011 & all but the BO started laying about a month ago. We've consistently been getting 2 blue eggs a day, with a brown egg every other day. In the last 2 days, we've gotten 1 brown & zero blues.

We've had solid food & water, so no issues there. The girls appear healthy & happy --they wait at the run door & make a racket whenever we're in the yard, in hopes of getting treats from the garden.

My question is this: Is Sept 5 in West MI really so dark, that light could be the culprit? Of course, it's only been 2 days, so am I jumping the gun on being worried? In any case, I had my husband put up a string of Christmas lights with a timer tonight --just in case. He's going to be really annoyed with me if he rushed to do that for nothing.

Also, just as a side note: any ideas on why the BO never started laying?